Caller-ID, also known as Caller-Identification (CID) or alternatively Calling Number Identification (CNID) is a public telephone service provided over the plain old telephone service (POTS) lines that transmits a caller's number to the called party's telephone equipment during the ringing signal, or when the call is being setup before the call is answered. Caller-ID can optionally provide a name, either personal or company, with the calling telephone number, with the Caller-ID information optionally being shown on the display on the called party's telephone.